Hi all,
I’m pretty new to dynamo and I’m trying to compose a list from families in my project. The objects have 2 custom parameters attached, a begin and a end date when they will be used. Now I want a unique list of all all those families with the same date and then get the total lengths. I have a list transpose that has all the dates sorted but I cant get a unique list from it. I want all “leuningplanken” with the same date in one list.
Can anyone help me out?
You could with List filter by keys on family name and Date, do you have a sample file for me to work with? (Revit 2018)
use List Sort by keys (i typed wrong in my img)
You could use list.contains and List.FilterByBoolMask with this you can search and filter for a date you want.
dont filter by keys but sort by keys srry 
this will group all “leuningplanken” by date
i did an example with a string “Leuningplank” but it will also work with elements:
it will group based on same date
I tried to upload the rvt but its to large.
Try uploading it to wetransfer or any other filesharing platform and share the link
This should do the trick 
If I list by “contains” I have to manually add every date which I try to avoid.
I seem to get an error that the number keys not matches the number of items. If i try it like this.
It should work. in sort by key node you see 3 groups and in the 2nd list you see 3 dates. group 1 is corresponding with date 1 and so on.
Its sorted on begin date now.
This picture probably explains better than i ever could 
if you want to filter on start and end date, you could use something like this:
If your thread is solved, please mark a post as solution 
After altering some levels and lacing I got my list thnx! The list groupbykey did the trick. Now I’m off to try and get al the lengths out of it and sort them on date. Wish me luck!
Good luck 
Tip: its allready sorted and you have the elements in the last node. you could just go on and get parameter value by name “Length” i suppose
